Generally, for example, as disclosed in JP-2001-246479A, an ultrasound joining method is provided to join two metal-made members. In this case, for example, the first member is constructed of a pipe (linear pipe) which has a flange portion at the one end side thereof. The second member is constructed of a wall surface of a header tank of a heat exchanger, for example.
The pipe (flange portion) is vibration-excited by a horn while being pressure-applied toward the side of the heat exchanger (wall surface of header tank) at a predetermined pressure, in such a state that the heat exchanger is fixed at an anvil. Thus, a friction is caused between the two members so that oxidation film of the two members is destroyed. In this case, clean contact surfaces of the two members which are emerging surfaces are extremely near to each other, so that the function among atoms occurs between the two members. Therefore, the flange portion is pressurized and joined to the wall surface of the header tank, due to the friction heat occurred at the contact surfaces of the two members and the function among atoms.
In this case, the horn contacts an outer surface (which is opposite to the side of heat exchanger) of the flange portion of the pipe, and has a cylindrical shape to cover the periphery of the pipe. As disclosed in JP-2001-246479A, the horn is set from the opposite side of the pipe (liner pipe) to the flange portion thereof.
However, according to the joining method disclosed in JP-2001-246479A, it is difficult to set the horn from the opposite side of the pipe to the flange portion in the case where the pipe has a bent portion or an overhang portion at the opposite side of the pipe to the flange portion.